Image forming device and method

ABSTRACT

Provided are an apparatus and a method of detecting an error in the apparatus. The apparatus includes an image former and an induction heating fusing device. The image former forms an image. The induction heating fusing device fuses the image formed by the image former onto paper. Whether the apparatus has an error is determined by limiting a current applied to a resonance circuit included in the induction heating fusing device to less than a certain level.

TECHNICAL FIELD

The present disclosure generally relates to an apparatus and a methodfor forming an image, and more particularly, to an apparatus and amethod for detecting an error.

BACKGROUND ART

Due to the development of technologies, a user may use a variety ofelectronic devices, and the electronic devices should work normallywithout an error occurring. However, it may be difficult for a user tocheck an error of an electronic device as the electronic device iscomplex.

If the electronic device keeps working abnormally, components of theelectronic device may become damaged and the electronic device may breakdown.

A lifespan of an electronic device may improve by detecting an error ofthe electronic device at an early stage. In order to detect an error ofthe electronic device, a component thereof, such as a circuit, may beexamined.

When a resonance circuit is used in an electronic device, an error ofthe resonance circuit may be detected so that dangers arising due toresonance of the resonance circuit are reduced.

An electromagnetic induction fusing device may employ an invertercontrolling method to detect an error of the resonance circuit.Characteristics of a resonance circuit may be determined based on Systemresistance Rs(Ω), coil inductance L(H), and capacitor capacitance C(F).

It is effective to drive a resonance circuit in its resonance frequency,but the resonance frequency may vary due to changes of characteristicsof each component.

When a driving frequency is lower than a resonance frequency, excesscurrent may flow through a resonance circuit or a circuit electricallyconnected to the resonance circuit, which may result in damage to thecircuits. Therefore, it is common to drive the resonance circuit at ahigher frequency than its resonance frequency. However, the resonancefrequency itself may rise somehow, and so the resonance circuit may bedriven at a lower frequency than its resonance frequency.

Technologies to solve such problems are disclosed in followingreferences:

Japanese Unexamined Patent Application Publication No. 03-190082

Japanese Unexamined Patent Application Publication No. 2008-053070

Japanese Unexamined Patent Application Publication No. 2008-197475

DISCLOSURE [Technical Problem]

The above references disclose methods of reducing the risk of excesscurrent flowing into a circuit in a device by driving the device or thecircuit in a frequency higher than its resonance frequency.

However, the frequency higher than the resonance frequency may not beguaranteed to be always higher than the resonance frequency since theresonance frequency may vary. Therefore, the risk of excess currentflowing into a circuit may still remain. For example, circuit componentsmay become damaged and their characteristics may change, which may allowthe excess current to flow into the circuit. For example, when a powersource is not consistent, the excess current may flow into the circuit.

According to an example embodiment, an induction heating fusing devicemay effectively reduce the risk of excess current flowing into acircuit.

[Technical Solution]

According to an aspect of an example embodiment, there is provided animage forming apparatus, including: an image former that forms an imageon printing paper; and an induction heating fusing device that fuses theimage onto the printing paper and includes: a resonance circuitincluding an inductor that is inductively heated by a current togenerate fusing heat; a driver circuit that applies a current to theresonance circuit; and a controller configured to drive the drivercircuit in an A-mode in which a fusing operation is performed, and todetermine whether the apparatus has an error in a B-mode in which amagnitude of the current applied to the resonance circuit by the drivercircuit is limited to less than a preset level.

The controller is configured to drive the driver circuit in the A-modewhen it is determined in the B-mode that the apparatus does not have anerror.

The driver circuit is supplied with power from different power sourcesrespectively in the A-mode and the B-mode.

The driver circuit includes a first driver circuit and a second drivercircuit, wherein the first driver circuit is driven in the A-mode, andthe second driver circuit is driven in the B-mode.

The driver circuit is alternatively electrically connected to the firstdriver circuit in the A-mode and the second driver circuit in theB-mode.

The first driver circuit is electrically separated from the seconddriver circuit, the first driver circuit is electrically open in theB-mode, and the second driver circuit is electrically open in theA-mode.

The controller is configured to determine whether the apparatus has anerror based on a power consumption value of at least one of theresonance circuit and the driver circuit.

The driver circuit is driven in the B-mode based on a first frequencyand a second frequency, and the power consumption value includes: afirst power consumption value that is estimated when the driver circuitis driven at the first frequency; and a second power consumption valuethat is estimated when the driver circuit is driven at the secondfrequency.

The controller is configured to determine whether the apparatus has anerror based on an inclination measured based on the first frequency, thefirst power consumption value, the second frequency, and the secondpower consumption value.

The driver circuit is driven in the A-mode at a driving frequency withina predetermined range, and the first frequency and the second frequencyis within the predetermined range.

The controller is configured to determine whether the apparatus has anerror based on a phase of a current in the resonance circuit.

The phase of the current in the driver circuit is detected periodicallybased on a clock of the controller.

The controller is further configured to determine whether the apparatushas an error in the A-mode, and to stop driving the driver circuit inthe A-mode when it is determined that the apparatus has an error.

The controller is configured to drive the driver circuit in the B-modeto determine whether the apparatus has an error when the controllerstops driving the driver circuit in the A-mode.

A driving frequency of the driver circuit in the A-mode is determinedbased on a power consumption value of at least one of the resonancecircuit and the driver circuit.

A driving frequency of the driver circuit in the A-mode is determinedbased on a phase of a current in the resonance circuit.

According to an aspect of another example embodiment, there is provideda method performed by an image forming apparatus including: an imageformer that forms an image on printing paper; and an induction heatingfusing device that fuses the image onto the printing paper and includes:a resonance circuit including an inductor that is inductively heated bya current to generate fusing heat; and a driver circuit that applies acurrent to the resonance circuit, wherein the method includes:determining whether the apparatus has an error in a B-mode in whichmagnitude of the current applied to the resonance circuit by the drivercircuit is limited to less than a preset level; and driving the drivercircuit in an A-mode in which a fusing operation is performed when it isdetermined that the apparatus does not have an error in the B-mode.

The driver circuit includes a first driver circuit and a second drivercircuit, wherein the first driver circuit is driven in the A-mode andthe second driver circuit is driven in the B-mode.

The determining includes: determining whether the apparatus has an errorbased on a power consumption value of at least one of the resonancecircuit and the driver circuit.

The determining includes: determining whether the apparatus has an errorbased on a phase of a current in the resonance circuit.

DESCRIPTION OF DRAWINGS

FIG. 1A illustrates an induction heating fusing device according to anexample embodiment.

FIG. 1B illustrates an induction heating fusing device including a firstdriver circuit and a second driver circuit, according to an exampleembodiment.

FIG. 1C illustrates a flowchart of a method of detecting an error in aninduction heating fusing device, according to an example embodiment.

FIG. 2 illustrates an induction heating fusing device according to anexample embodiment.

FIG. 3A illustrates an example table regarding a relationship betweendriving frequencies and power consumption values.

FIG. 3B illustrates a graph regarding a relationship between drivingfrequencies and power consumption values.

FIG. 4 illustrates a flowchart of a driving process performed in aninduction heating fusing device, according to an example embodiment.

FIG. 5 illustrates a flowchart of a method for detecting an error in aninduction heating fusing device of a B-mode, according to an exampleembodiment.

FIG. 6 illustrates an example graph showing a relationship betweendriving frequencies and power consumption values, according to voltagechanges of a power source.

FIG. 7 illustrates an induction heating fusing device according to anexample embodiment.

FIG. 8 illustrates an example table showing a relationship betweendriving frequencies and current phases.

FIG. 9 illustrates an example graph showing a relationship betweendriving frequencies and current phases.

FIG. 10 illustrates a flowchart of a driving process performed in aninduction heating fusing device, according to an example embodiment.

FIG. 11 illustrates a flowchart of a driving process performed in aninduction heating fusing device, according to an example embodiment.

FIG. 12 illustrates an image forming apparatus according to an exampleembodiment.

MODE FOR INVENTION

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings. In this regard, thepresent embodiments may have different forms and should not be construedas being limited to the descriptions set forth herein. However, theexample embodiments may be realized in different forms, and are notlimited to the embodiments in the present disclosure. In theaccompanying drawings, like reference numerals refer to like elementsthroughout.

All terms including descriptive or technical terms which are used hereinshould be construed as having meanings that are obvious to one ofordinary skill in the art. However, the terms may have differentmeanings according to the intention of one of ordinary skill in the art,precedent cases, or the appearance of new technologies. Also, some termsmay be arbitrarily selected by the applicant, and in this case, themeaning of the selected terms will be described in detail in thedetailed description. Thus, the terms used herein have to be definedbased on the meaning of the terms together with the descriptionthroughout the specification.

As used herein, the singular forms “a”, “an”, and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It should be understood that the terms “comprises,”“comprising,” “including,” and “having” are inclusive and thereforespecify the presence of stated features or components, but do notpreclude the presence or addition of one or more other features orcomponents. Numbers described herein are examples for helpingunderstanding, and embodiment should not be limited to the numbers.

In the present disclosure, the term such as “ . . . unit” or “ . . .module” should be understood as a unit in which at least one function oroperation is processed A component termed as “ . . . unit” or “ . . .module” may be embodied as hardware, software, or a combination ofhardware and software.

It should be understood that, although the terms “first,” “second,” etc.may be used herein to describe various elements, and these elementsshould not be limited by these terms. These terms are used todistinguish one element from another. For example, a first element maybe termed a second element within the technical scope of an exampleembodiment.

FIG. 1A illustrates an induction heating fusing device according to anexample embodiment.

As illustrated in FIG. 1A, an induction heating fusing device 100 aincludes a resonance circuit, a driver circuit 23, and a controller 10.

The induction heating fusing device 100 a may be provided with an imageforming apparatus such as a laser printer, and may be used to fuse toneronto paper in the laser printer.

The induction heating fusing device 100 a may drive the driver circuit23 to detect an error of the resonance circuit and/or the driver circuit23.

The induction heating fusing device 100 a may perform a fusing operationbased on determining whether the induction heating fusing device 100 aor the resonance circuit thereof has an error in a condition wheremagnitude of a current applied to the resonance circuit by the drivercircuit 23 is limited to less than a preset level.

According to the induction heating fusing device 100 a, whether thedevice 100 a or the resonance circuit thereof has an error is determinedin a condition where magnitude of a current applied to the resonancecircuit by the driver circuit 23 is limited to less than a preset level,and damage from an excess current may be reduced.

The resonance circuit of the induction heating fusing device 100 a mayinclude an inductor generating a fusing heat by a flow of electricity.For example, as illustrated in FIG. 1A, the resonance circuit may be aserial LC circuit including a capacitor 15 and a coil 16 that areconnected in serial, but is not limited thereto.

The resonance circuit may resonate based on its resonance frequency. Theresonance frequency may be determined based on inductance andcapacitance of the resonance circuit and the driver circuit 23electronically connected to the resonance circuit.

When characteristics of components of the resonance circuit or thedriver circuit 23 change due to damage, aging, or degradation, theresonance frequency may vary.

The driver circuit 23 of the induction heating fusing device 100 a maybe electronically connected to the resonance circuit, and driven at adriving frequency by the controller 10. A current or voltage of thedriving frequency may be applied to the resonance circuit by driving thedriver circuit 23. The driver circuit 23 may be connected to a powersupply.

When the driver circuit 23 is driven at a frequency lower than theresonance frequency, an excess current may flow into the driver circuit23 or the resonance circuit connected thereto. As described above, theresonance frequency may vary when characteristics of components of theresonance circuit or the driver circuit 23 change, and thus, the drivercircuit 23 may be driven at a driving frequency lower than the resonancefrequency.

The controller 10 of the induction heating fusing device 100 a mayacquire information from a memory, an input port, a current detector, ora voltage detector to perform an operation. The controller 10 may storeinformation in a memory or drive a circuit based on a performedoperation. The controller 10 may control a switch of the circuit.Operations may be performed based on a program stored in a memory. Thecontroller 10 may be a micro-controller or a micro computer, but is notlimited thereto.

The controller 10 may drive the driver circuit 23. For example, thecontroller 10 may control a switch of the driver circuit 23.

The controller 10 may drive the driver circuit to apply a voltage to theresonance circuit or let a current flow through the resonance circuit.For example, the controller 10 may apply a voltage of a certainfrequency to the resonance circuit or let a current of a certainfrequency flow through the resonance circuit by driving the drivercircuit 23.

The controller 10 may drive the driver circuit 23 in an A-mode and aB-mode. The A-mode may be referred to as a normal driving mode, and theB-mode may be referred to as a test driving mode. A frequency drivingthe driver circuit 23 in the A-mode may be referred to as a drivingfrequency, and a frequency driving the driver circuit 23 in the B-modemay be referred to as a test driving frequency, but roles of thefrequencies are not limited by their names herein.

A fusing operation may be performed in the A-mode by the driver circuit23 and the resonance circuit electrically connected thereto. A magneticfield is generated by a current of a driving frequency flowing throughan induction heating (IH) coil of the resonance circuit, and a fusingroller is heated by the magnetic field to fuse toner onto paper.

The controller 10 may determine whether the induction heating fusingdevice 100 a has an error by driving the driver circuit 23 in theB-mode. When it is determined that the induction heating fusing device100 a does not have an error, the controller 10 may drive the drivercircuit 23 in the A-mode.

Magnitude of a current flowing through the resonance circuit in theB-mode may be limited to less than a preset level, and thus, magnitudeof the current in the B-mode may be smaller than in the A-mode. Thedriver circuit 23 may be provided with power from different powersources respectively in the A-mode and the B-mode, and thus magnitude ofthe current flowing through the resonance circuit may be limited to lessthan a preset level. For example, a voltage between 3 V and 5 V may beapplied to the driver circuit 23 in the B-mode, and a voltage between100 V and 200 V may be applied to the driver circuit 23 in the A-mode.

According to an example embodiment, the magnitude of the current in theB-mode is relatively small, and risk of an excess current may be reducedeven while the driver circuit 23 is driven at a frequency lower than theresonance frequency.

The driver circuit 23 may include a first driver circuit and a seconddriver circuit, which will be described with reference to FIG. 1B.

FIG. 1B illustrates an induction heating fusing device including a firstdriver circuit and a second driver circuit, according to an exampleembodiment.

Referring to FIG. 1B, an induction heating fusing device 100 b mayinclude a controller 10, a first driver circuit 20, a second drivercircuit 30, a resonance circuit, and a switch 14 electrically connectingthe resonance circuit with the first driver circuit 20 or the seconddriver circuit 30.

According to an example embodiment, the controller 10 may control theswitch 14 to electronically connect the resonance circuit alternatelywith the first driver circuit 20 and the second driver circuit 30.

According to an example embodiment, the first driver circuit 20 may bedriven in the A-mode, and the second driver circuit 30 may be driven inthe B-mode. The first driver circuit 20 may be referred to as a normaldriver circuit, and the second driver circuit 30 may be referred to as atest driver circuit, but the roles of the circuits are not limited bytheir names.

The controller 10 may drive the second driver circuit in the B-mode andcontrol the switch to electronically connect the resonance circuit withthe second driver circuit 30. The controller 10 may determine whetherthe induction heating fusing device 100 b has an error by driving thesecond driver circuit 30 in the B-mode. When it is determined that theinduction heating fusing device 100 b does not have an error, thecontroller 10 may control the switch 14 to electrically connect theresonance circuit with the first driver circuit 20 and drive the firstdriver circuit in the A-mode.

According to an example embodiment, the risk of damaging the firstdriver circuit 20 due to an excess current may be reduced by determiningwhether the induction heating fusing device 100 b has an error by thesecond driver circuit 30 in the B-mode.

According to an example embodiment, the risk of damaging the firstdriver circuit 20 due to an error in power may be reduced.

FIG. 1C illustrates a flowchart of a method of detecting an error in aninduction heating fusing device according to an example embodiment.

In operation S100, the induction heating fusing device may determinewhether the device has an error in the B-mode in which magnitude of acurrent applied to a resonance circuit by the driver circuit is limitedto less than a preset level.

The driver circuit may be driven by a test driving frequency. The testdriving frequency may be higher than a predetermined frequency within arange of driving frequencies of the A-mode. For example, thepredetermined frequency within the range of the driving frequencies maybe at half, two thirds, three quarters, or four fifths of the range, butis not limited thereto.

According to an example embodiment, whether the induction heating fusingdevice 100 b has an error may be determined by detecting a current orvoltage applied to a resonance circuit, or by detecting a currentflowing through a coil 16 of the resonance circuit or a voltage betweenboth ends of the coil 16. Example methods of determination of an errorare described later with reference to FIGS. 3A, 3B, 8B, and 9.

In operation S110, when it has been determined in operation S100 thatthe device does not have an error, the induction heating fusing devicemay drive a driver circuit in the A-mode in which a fusing operation isperformed

Magnitude of a current flowing through the resonance circuit in theB-mode may be limited to less than a preset level, and thus, magnitudeof the current in the B-mode may be smaller than the A-mode. The drivercircuit may be provided with power from different power sourcesrespectively in the A-mode and the B-mode, and thus magnitude of thecurrent flowing through the resonance circuit may be limited to lessthan a preset level. For example, a voltage between 3 V and 5 V may beapplied to the driver circuit in the B-mode, and a voltage between 100 Vand 200 V may be applied to the driver circuit in the A-mode.

FIG. 2 illustrates an induction heating fusing device according to anexample embodiment.

According to an example embodiment, an induction heating fusing device 1may include a controller 10, a normal driver circuit 20, a test drivercircuit 30, a relay circuit controlling power supplied from a powersource 2, a current detector 50, a voltage detector 60, a fusing roller90, a resonance circuit including a capacitor 15 and an IH coil 16, anda switch 14 for switching between the normal driver circuit 20 and thetest driver circuit 30. So that rectification, smoothing, and noisefiltering of a current from the power source 2 may be carried out, theinduction heating fusing device 1 may further include a diode bridge 11,a coil 12, and a capacitor 13.

Both of the normal driver circuit 20 and the test driver circuit 30 maybe used for resonance of the resonance circuit including the capacitor15 and the IH coil 16. The normal driver circuit 20 may be used in theA-mode (normal driving mode) to fuse toner onto paper, and the testdriver circuit 30 may be used in the B-mode (test driving mode) to checkerrors of components of the resonance circuit and the induction heatingfusing device 1.

The normal driver circuit 20 may include a gate driver integratedcircuit (IC) 21 and a switching component 22 which may be an insulatedgate bipolar mode transistor. The gate driver IC 21 may switch theswitching component 22, and thereby the normal driver circuit 20 may bedriven at a driving frequency in the A-mode based on a controlinstruction from the controller 10 to apply a voltage or current to theresonance circuit.

The normal driver circuit 20 may be provided with a certain amount ofpower that is, for example, more than 100 W, and a certain voltage of100-200V may be applied to the normal driver circuit 20 afterrectification, smoothing, and noise filtering processes.

The test driver circuit 30 may include an operational amplifier(OP-amp), a capacitor, and a resistor, but is not limited thereto. Thetest driver circuit 30 may be driven at a test driving frequency in theB-mode based on a control instruction from the controller to apply avoltage or current to the resonance circuit.

The normal driver circuit 20 may be used for a normal driving mode wheretoner is fused onto paper, and the test driver circuit 30 may be drivenat a test driving frequency that is higher than a certain frequency in arange of driving frequencies to determine whether the induction heatingfusing device 1 has an error.

The test driver circuit 30 may be provided with power via a differentline from the normal driver circuit 20. For example, a voltage between3V and 5V may be applied to the test driver circuit 30, and a voltagebetween 100V and 200V may be applied to the normal driver circuit 20.Therefore, a current flowing through the resonance circuit from the testdriver circuit 30 in the B-mode may be limited to less than apredetermined level, and thereby magnitude of the current in the B-modemay be smaller than that in the A-mode.

Through the switch 14, the normal driver circuit 20 and the test drivercircuit 30 may be alternately connected to the resonance circuitincluding the capacitor 15 and the IH coil 16. The switch 14 may beswitched by receiving a control instruction from the controller 10.

The controller 10 may measure a power consumption value based on acurrent and a voltage detected by the current detector 50 and thevoltage detector 60. A unit including the controller 10, the currentdetector 50, and the voltage detector 60 may be referred to as a powermeasurer.

Referring to FIG. 2, the normal driver circuit 20 and the test drivercircuit 30 are provided with power from different lines, and a powerconsumption value may be measured respectively in the A-mode and theB-mode.

Referring to FIG. 2, a power consumption value in the A-mode may bemeasured by detecting a current from a line connected to the powersource 2 and a voltage from a power supply line connected to theresonance circuit.

The controller 10 may determine whether the induction heating fusingdevice 1 has an error based on the measured power consumption value.

An example method of determining an error is described with reference toFIGS. 3A and 3B.

FIG. 3A illustrates an example table regarding a relationship betweendriving frequencies and power consumption values.

FIG. 3B illustrates an example graph regarding a relationship betweendriving frequencies and power consumption values.

To determine whether the induction heating fusing device 1 has an error,the controller 10 may refer to a table 101 regarding a relationshipbetween power and driving frequencies as illustrated in FIG. 3A.

The table 101 may store information regarding expected power consumptionvalues with respect to driving frequencies.

The table 101 may be stored in a memory of the controller 10 or theinduction heating fusing device 1.

The controller 10 may determine whether the induction heating fusingdevice 1 has an error based on a measured power consumption value andthe table 101. For example, when the measured power consumption value is100 W at a test driving frequency of 90 KHz of the B-mode, thecontroller 10 may determine that the induction heating fusing device 1has an error. When the measured power consumption value exceeds apredetermined range relative to the expected power at the test drivingfrequency, it may be determined that the device has an error.

According to an example embodiment, the controller 10 may determinewhether the induction heating fusing device 1 has an error based on aplurality of test driving frequencies in the B-mode. For example,expected power consumption values at test driving frequencies of f1 (75kHz) and f2 (70kHz) are respectively 120 W and 170 W, and it may bedetermined that the induction heating fusing device 1 has an error whenan inclination between measured power consumption values with respect tothe test driving frequencies differs by more than a certain extent froman inclination between the expected power consumption values withrespect to the same test driving frequencies. Here, the inclination ofthe expected power consumption values of 120 W and 170 W with respect tothe test driving frequencies of 75 KHz and 70 KHz is −10 where units areomitted.

According to an example embodiment, the table 101 may be generated orset based on a graph regarding a relationship between power consumptionvalues and driving frequencies illustrated in FIG. 3B. Referring to FIG.3B, the graph may be determined based on design of the induction heatingfusing device 1.

A driving range of driving frequencies in the A-mode by the normaldriver circuit 20 and a driving range of driving frequencies in theB-mode by the test driver circuit 30 are illustrated in FIG. 3B.According to an example embodiment, the controller 10 may determinewhether the induction heating fusing device 1 has an error based on aplurality of test driving frequencies in the B-mode. The plurality oftest driving frequencies, such as two test driving frequencies f1 and f2may be higher than a predetermined driving frequency within the drivingrange of the driving frequencies in the A-mode. The test drivingfrequencies f1 and f2 in the B-mode may be within the driving range ofthe driving frequencies in the A-mode.

In the present disclosure, a resonance frequency f0 is 34.1 KHz, and thetest driving frequencies f1 and f2 are respectively 75 KHz and 70 KHz,but are not limited thereto.

According to an example embodiment, whether the induction heating fusingdevice 1 has an error may be determined based on measured powerconsumption values.

FIG. 4 illustrates a flowchart of a driving process performed in aninduction heating fusing device according to an example embodiment.

An explanation of the flowchart will be provided with further referenceto FIG. 1C. Processes explained below may be performed by the controller10 of the induction heating fusing device 1.

According to an example embodiment, the induction heating fusing device1 may be included in an image forming apparatus such as a laser printerand receive a request of a printing operation based on a user input. Inoperation S401, the induction heating fusing device 1 may acquire atarget power consumption value necessary for the printing operation.

Information about the target power consumption value may be included inthe request of the printing operation.

In operation S402, the induction heating fusing device 1 may determinewhether the induction heating fusing device 1 is in a booting process.The booting process may start when the induction heating fusing device 1starts booting and end after a predetermined time, or start when theinduction heating fusing device 1 starts returning from standby and endafter a predetermined time, but is not limited thereto.

The next operation of the method is operation S403 when the inductionheating fusing device 1 is in the booting process, or operation S406when the induction heating fusing device 1 is not in the bootingprocess.

In operation S403, the induction heating fusing device 1 may control theswitch 14 to electronically connect the resonance circuit with the testdriver circuit 30. When the resonance circuit is connected to the normaldriver circuit 20, the induction heating fusing device 1 mayelectrically separate the resonance circuit from the normal drivercircuit 20 and electrically connect the resonance circuit to the testdriver circuit 30.

The resonance circuit may be electronically separated from a power lineapplying a voltage such as one between 100V and 200V from the normaldriver circuit 20, and electronically connected to a power line applyinga voltage such as one between 3V and 5V from the test driver circuit 30.Because the resonance circuit is electrically separated from the normaldriver circuit 20, the risk of an excess current flowing into theswitching component 22 of the normal driver circuit 20 may be reduced.

In operation S404, the induction heating fusing device 1 may perform anoperation in the B-mode. An explanation of the operation in the B-modewill be provided with reference to FIG. 5.

FIG. 5 illustrates a flowchart of a method for detecting an error in aninduction heating fusing device of the B-mode, according to an exampleembodiment.

In operation S501, the induction heating fusing device 1 may drive thetest driver circuit 30 at a test driving frequency f1 (75 KHz).

In operation S502, the induction heating fusing device 1 may acquire apower consumption value P1 according to the test driving frequency f1.The induction heating fusing device 1 may detect a current and a voltageapplied to the resonance circuit in the B-mode, or detect a currentflowing through the IH coil 16 of the resonance circuit and a voltagebetween both ends of the IH coil 16.

In operation S503, the induction heating fusing device 1 may drive thetest driver circuit 30 at a test driving frequency f2 (70 KHz). Inoperation S504, the induction heating fusing device 1 may acquire apower consumption value P2 according to the test driving frequency f2.The explanation provided with respect to operations S501 and S502 may beapplied to operations S503 and S504, and thus redundant explanations areomitted.

In operation S505, the induction heating fusing device 1 may calculatean inclination between power consumption values with respect to drivingfrequencies based on the measured power consumption values P1 and P2 andthe driving frequencies f1 and f2.

Power consumption values expected from two driving frequencies f1 (75KHz) and f2 (70 KHz) are respectively 120 W and 170 W, and there is aninclination between the expected power consumption values with respectto driving frequencies. For example, the inclination may be −10 whereunits are omitted.

In operation S506, the induction heating fusing device 1 may determinewhether the inclination is within a normal range. The normal range ofthe inclination may be set by a parameter that is fixed or changeable.

It may be determined that the induction heating fusing device 1 has anerror when an inclination between measured power consumption values withrespect to test driving frequencies exceeds a predetermined value orrange. For example, referring to the graph of FIG. 3B, when the testdriving frequencies f1 and f2 are respectively 75 KHz and 70 KHz,corresponding expected power consumption values P1 and P2 arerespectively 120 W and 170 W. Here, an inclination between the expectedpower consumption values P1 and P2 is −10 where units are omitted, andit may be determined that the induction heating fusing device 1 has anerror when the inclination between the measured power consumption valueswith respect to the test driving frequencies f1 and f2 (75 KHz and 70KHz) is outside of a normal range determined based on the inclinationbetween the expected power consumption values P1 and P2.

As a result of the determination in operation S506, the inductionheating fusing device 1 outputs an okay (OK) signal when the inclinationbetween the measured power consumption values is within the normalrange, and outputs a no good (NG) signal when the inclination is outsidethe normal range.

Referring back to FIG. 4, based on a signal output by the inductionheating fusing device 1 in operation S405, the next operation of themethod is operation S406 when the output signal is an OK signal, or thenext operation of the method is operation S412 when the output signal isan NG signal.

In operation S412, the induction heating fusing device 1 may stopdriving the test driver circuit 30. Accordingly, an output to anoscillating circuit may be prevented from being sent. An instruction tostop driving the test driver circuit 30 may include at least one fromamong an instruction for the test driver circuit 30 to stop oscillation,an instruction to open the relay circuit 40, and an instruction to openthe switch 14, but is not limited thereto.

In operation 413 where an NG signal is output, the device may performerror processing. For example, an error message may be displayed. Inoperation S413, when an error occurs, the induction heating fusingdevice 1 may store information regarding a status of the inductionheating fusing device 1 such as test driving frequencies, detectedcurrent, detected voltage, or temperature. The information may be usedfor analysis of errors.

In operation S406 performed after an OK signal is output, the inductionheating fusing device 1 may control the switch 14 to electronicallyconnect the resonance circuit with the test driver circuit 20.

In operation S407, the induction heating fusing device 1 may perform anoperation in the A-mode.

The normal driver circuit 20 may be driven at a driving frequency thatcorresponds to the acquired target power consumption value necessary forthe printing operation. The driving frequency that corresponds to theacquired target power consumption value may be acquired from the table101 of FIG. 3A.

According to an example embodiment, the induction heating fusing device1 may determine whether the induction heating fusing device 1 or theresonance circuit has an error while operating in the A-mode.

In operation S408, the induction heating fusing device 1 may detect acurrent and a voltage from the current detector 50 and the voltagedetector 60 to measure a power consumption value, and determine whetherthe induction heating fusing device 1 has an error by comparing themeasured power consumption value with an expected power consumptionvalue.

When the measured power consumption value is outside a normal rangedetermined based on the expected power consumption value, the nextoperation of the method is S412 for stopping an output from being sentto an oscillating circuit, and the following operation is S413 forperforming error processing. An instruction to stop driving of thenormal driver circuit 20 may include at least one from among aninstruction for the normal driver circuit 20 to stop oscillation, aninstruction to open the relay circuit 40, and an instruction to open theswitch 14, but is not limited thereto.

When it is determined that the measured power consumption value of anoperation in the A-mode is within the normal range, the inductionheating fusing device 1 may determine whether the printing operation hasbeen completed in operation S410. When the printing operation has notbeen completed, the method moves back to operation S407 to continue theprinting operation in the A-mode. When the printing operation has beencompleted, the method moves onto operation S411 to perform endingprocessing such as suspension of driving of the normal driver circuit 20and recording of result data.

According to an example embodiment, the risk of an excess currentflowing into the normal driver circuit 20 or the switching component 22thereof may be reduced because the induction heating fusing device 1performs test driving in the B-mode when booted.

In general, in order to reduce the risk of an excess current, a drivercircuit is driven at a frequency higher than its resonance frequency.However, it is also possible that the driver circuit may be driven at afrequency lower than its resonance frequency due to an error in theinduction heating fusing device 1. If the driver circuit is driven by afrequency lower than its resonance frequency, an excess current may flowinto the circuit.

According to an example embodiment, an operation in the B-mode (testdriving mode) is performed by the test driver circuit 30 when theinduction heating fusing device 1 or an image forming apparatusincluding the device is booted, and an excess current, and thus, therisk of damaging the circuit may be reduced even though a drivingfrequency is lower than the resonance frequency. The normal drivercircuit 20 including the switching component 22 may be open-circuited inthe B-mode so as to reduce the risk of an excess current flowing intothe normal driver circuit 20.

When characteristics of components of the induction heating fusingdevice 1 change due to damage, aging, or degradation, an error may occurin the induction heating fusing device 1.

When the power source 2 has an error, an excess current may flow into acircuit. An explanation of an error of a power source will be providedwith reference to FIG. 6.

FIG. 6 illustrates an example graph regarding a relationship betweendriving frequencies and power consumption values, according to voltagechanges of a power source.

The graph of FIG. 6 illustrates a case in which a voltage of a powersource is changed to 180 V, 230 V, and 280 V. For example, when adriving frequency is 50 KHz and a power source is also changed to 420 W,710 W, and 1042 W, corresponding expected power consumption values arerespectively 420 W, 710 W, and 1042 W. Therefore, the induction heatingfusing device 1 may have an error when a power source fails to supply astable voltage.

According to an example embodiment, a test operation in the B-mode isperformed by the test driver circuit 30 while a voltage of a powersource varies, and thus, the risk of circuit damage may be reduced.

As described above, an inclination between power consumption values withrespect to driving frequencies is acquired in the B-mode, and an errorof the induction heating fusing device 1 may be determined based on theacquired inclination. As illustrated in FIG. 3B, a gradient of a powerconsumption value with respect to a driving frequency becomes greater asthe driving frequency approaches a resonance frequency f0. Therefore,when agradient of a measured power consumption value with respect to adriving frequency is greater than an inclination of a expected powerconsumption value with respect to the same driving frequency, it may bedetermined that the induction heating fusing device 1 is in an errorstate or the induction heating fusing device 1 nears the error state.

A characteristic of a relationship between a power consumption value anda driving frequency may be determined by measuring power consumptionvalues with respect to two driving frequencies f1 and f2 and calculatingan inclination of the power consumption values with respect to the twodriving frequencies. However, the characteristic of the relationship maybe determined by various methods.

For example, the characteristic of the relationship may be determined bymeasuring power consumption values with respect to a plurality ofdriving frequencies.

When a measured power consumption value with respect to a test drivingfrequency exceeds or is outside a range determined based on an expectedpower consumption value with respect to the same test driving frequency,it may be determined the induction heating fusing device 1 has an error.Furthermore, the controller 10 may determine whether the inductionheating fusing device 1 has an error based on the aforementioned method.

According to an example embodiment, an operation in the B-mode may beperformed when the induction heating fusing device 1 is booted,regardless of a request of a printing operation.

According to an example embodiment, an operation in the B-mode may beperformed as a request of a printing operation is received, regardlessof booting of the induction heating fusing device 1. For example, a testoperation may be performed in the B-mode when the induction heatingfusing device 1 is not in a printing operation, for example, in an idlestate.

According to an example embodiment, a state where the test drivercircuit 30 is electrically connected to the resonance circuit may be setas a default state of the induction heating fusing device 1. Here,operation S403 in which the test driver circuit 30 is connected to theresonance circuit by the switch 14 when the induction heating fusingdevice 1 is booted may be omitted. Therefore, stability of the inductionheating fusing device 1 may improve.

According to FIG. 5, it is illustrated that the induction heating fusingdevice 1 includes the normal driver circuit 20 and the test drivercircuit 30 to perform the test operation, but the test operation may beperformed by switching of a power source line without the test drivercircuit 30. For example, the normal driver circuit 20 may be alternatelyconnected to each power line, one of the power lines being for a normaloperation in which a voltage between 100V and 200V is applied, andanother of the power lines being for the test operation in which avoltage between 3V and 5V is applied. The normal driver circuit 20 mayfunction as the test driver circuit 30 when the normal driver circuit 20is connected to the power line for the test operation.

In the present disclosure, the normal driver circuit 20 and the testdriver circuit 30 are explained as they are separate. However, it shouldbe understood that the normal driver circuit 20 and the test drivercircuit 30 physically and separately exist. For example, an integratedchip may employ both of the normal driver circuit 20 and the test drivercircuit 30.

FIG. 7 illustrates an induction heating fusing device according to anexample embodiment.

As illustrated in FIG. 7, an induction heating fusing device 1′ mayfurther include a current phase detector 70.

The current phase detector 70 may detect a phase of a driving currentflowing through the resonance circuit and a phase of a driving voltage.The detected phase of the driving current and a zero-cross phase may becompared with each other so that the current phase detector 70 mayacquire a phase difference.

Information regarding the phase of the current may be acquired by a timemeasuring socket of the controller 10. Information regarding the phaseof the current may be periodically acquired by the current phasedetector 70 based on a clock frequency of the controller 10.

An example method of determining an error based on a phase of a currentshall be described with reference to FIGS. 8 and 9.

FIG. 8 illustrates an example table regarding a relationship betweendriving frequencies and current phases.

FIG. 9 illustrates an example graph regarding a relationship betweendriving frequencies and current phases.

To determine whether the induction heating fusing device 1 has an error,the controller 10 may refer to a table 102 regarding a relationshipbetween current phase values and driving frequencies as illustrated inFIG. 8. The table 101 may store information regarding current phasevalues with respect to driving frequencies, and may be stored in amemory of the controller 10 or the induction heating fusing device 1′.

The table 102 may be generated, set, or determined based on a graphregarding a relationship between current phase values and drivingfrequencies illustrated in FIG. 9. Referring to FIG. 9, the graph may bedetermined based on a design of the induction heating fusing device 1′.

Referring to FIG. 9, the graph illustrates a characteristic of arelationship between driving frequencies and system impedance of acurrent phase when the induction heating fusing device 1′ is booted. Forexample, a current phase is 0° at a driving frequency of 32.68 KHz whichis the resonance frequency.

FIG. 10 illustrates a flowchart of a driving process performed in aninduction heating fusing device, according to an example embodiment.

An explanation of the flowchart shall be provided with further referenceto FIG. 7. Processes explained below may be performed by the controller10 of the induction heating fusing device 1′.

An explanation with respect to the same operations in FIG. 4 is omitted.According to an example embodiment, the induction heating fusing device1′ may be included in an image forming apparatus such as a laser printerand receive a request of a printing operation based on a user input.

In response to the request of the printing operation, the inductionheating fusing device 1′ or the image forming apparatus including thedevice 1′ may perform an operation in the B-mode, and proceed to theA-mode when the induction heating fusing device 1′ is not in an errorstate, or perform error processing when the induction heating fusingdevice 1′ is in an error state.

In operation S407, the induction heating fusing device 1′ may perform anoperation in the A-mode. In operation S1001, the current phase detector70 may detect a current phase.

In operation S1002, the induction heating fusing device 1′ may determinewhether the detected current phase is within a normal range.

Standards of determining whether the detected current phase is withinthe normal range may be set by a parameter that is fixed or changeable.For example, the detected current phase at a driving frequency may becompared with a expected current phase corresponding to the same drivingfrequency based on the table 102, and it may be determined that theinduction heating fusing device 1′ has an error when a differencebetween the detected current phase and the expected current phaseexceeds a certain difference such as ±5°. It may be determined that theinduction heating fusing device 1′ has an error when the detectedcurrent phase itself is smaller than a certain value such as 10°.Furthermore, a combination of the above two standards may be considered.Also, it may be determined that the induction heating fusing device 1′has an error when the detected current phase is smaller than the certainvalue, but even when the detected current phase is greater than thecertain value, when the difference between the detected current phaseand the expected current phase exceeds the certain difference, it may bedetermined that the induction heating fusing device 1′ has an error.

As a result of the determination in operation S1002, the method proceedsto operation S412 to stop driving and perform the error processing whenthe induction heating fusing device 1′ has an error.

Otherwise, the method proceeds to operations S408 and S409 to measure apower consumption value and determine whether the acquired powerconsumption value is within a normal range. The method further proceedsto operation S1003 when the acquired power consumption value is withinthe normal range.

When expected values according to the tables 101 and 102 differ frommeasured values by more than a certain extent, the induction heatingfusing device 1′ may acquire a parameter for correction based on themeasured values.

In operation S408, a difference between the measured power consumptionvalue and the expected measured values with respect to the same drivingfrequency may be acquired. For example, when the normal driver circuit20 is driven at a driving frequency of 44.5 KHz, its expected powerconsumption value is 700 W according to the table 101. However, when itsmeasured power consumption value is 680 W, a correction corresponding toa difference ΔP between the measured power consumption value and theexpected power consumption value, which is 20 W, may be added to thedriving frequency of 44.5 KHz. If a target power consumption value is700 W at the driving frequency of 44.5 KHz, the driving frequency may becorrected to perform an operation at the target power consumption value.

Correction of the driving frequency may be made based on the table 101.For example, a frequency resolution is calculated based on the drivingfrequency of the target power consumption value, and then, multiplied bythe difference ΔP between the target power consumption value and themeasured power consumption value at the driving frequency and afrequency correction gain Kp to determine a corrected driving frequency.The frequency correction gain Kp may be determined based on anexperiment. The frequency correction gain Kp may be 1.75, but is notlimited thereto.

A correction parameter may be determined by multiplying a frequencyresolution near the target power consumption value, the difference ΔP,and the frequency correction gain Kp.

For example, when the measured power consumption value is 20 W lowerthan the target power consumption value of, for example, 700 W at thedriving frequency of 44.5 KHz, and a power consumption value near thetarget power consumption value is 800 W which corresponds to a drivingfrequency of 43.8 KHz, the frequency resolution near the target powerconsumption value may be acquired by equation 1.

[44.5 (KHz)−43.8 (KHz)]/[700 (W)−800 (W)]=−0.007 (KHz/W)   (1)

The acquired frequency resolution −0.007 KHz/W may be multiplied by thedifference ΔP of 20 W and the frequency correction gain Kp of 1.75 toacquire a correction parameter of −0.25 KHz, and the table 101 may becorrected based on the correction parameter of −0.25 KHz.

When a target power consumption value is 700 W, its correspondingdriving frequency is 44.5 KHz. However, the correction parameter of−0.25 KHz may be added to the driving frequency of 44.5 KHz, and so thecorrected driving frequency may be 44.25 KHz and be used for driving acircuit in the induction heating fusing device 1′.

The corrected driving frequency may be calculated by Equation 2.

The corrected driving frequency={[(Y1−Y2)/(X1−X2)]*ΔP*Kp}+Y1   (2)

Here, Y1 is a driving frequency, X1 is a power consumption valuecorresponding to the driving frequency Y1, Y2 and X2 are valuesapproximate to the driving frequency Y1 and the power consumption valueX1, ΔP is a difference between a measured power consumption value and anexpected power consumption value, and Kp is a correction parameter.

Correction of a driving frequency may be made based on the table 102.For example, referring to FIG. 8, when an expected current phase is 55°at a driving frequency of 43.21 KHz, and a correction parameter is 1.8KHz, a driver circuit may be driven at a corrected driving frequency of45.0 KHz that is a sum of the original driving frequency of 43.21 KHzand the correction parameter of 1.8 KHz, and thus, a correspondingcurrent phase is determined as 60°. Whether the induction heating fusingdevice 1′ has an error may be determined based on a difference betweenthe determined current phase of 60° and a measured current phase.

After the correction parameter is calculated in operation S1003,operations in the induction heating fusing device 1′ may be performedbased on the corrected driving frequency.

In an example embodiment, the correction parameter may be updated whilerepeating operations S407 through S410, and the driving frequency may becorrected according to the updated correction parameter.

According to an example embodiment, the risk of operating at a lowerfrequency than a resonance frequency may be reduced by determiningstability of the induction heating fusing device 1′ in the A-mode basedon a difference between a measured current phase and an expected currentphase.

As a driving frequency becomes closer to a resonance frequency, a phasedifference becomes smaller. Therefore, whether the driving frequency isclose to the resonance frequency may be determined based on the phasedifference, and thus, the risk of driving a driver circuit at a lowerfrequency than the resonance frequency may be reduced.

According to an example embodiment, a phase of a current may be detectedperiodically based on a clock of the controller 10, which may acceleratea test procedure in comparison with signal synchronization based onzero-crossing. Furthermore, when the induction heating fusing device 1′has an error, a stop process may be performed immediately, and thus, therisk of damaging circuits of the device may be reduced.

According to an example embodiment, the induction heating fusing device1′ may operate in a stable condition, even as characteristics ofcomponents of the induction heating fusing device 1′ change, bycalculating and updating a correction parameter frequently.

According to an example embodiment, calculation of the correctionparameter (operation S1003) may be performed in the B-mode. For example,a driver circuit is driven at a test driving frequency to calculate apower consumption value at the test driving frequency as in operationsS501 through S504, and then, calculation of the correction parameter maybe performed.

Accordingly, the correction parameter may be acquired before theinduction heating fusing device 1′ proceeds to the A-mode, so thatoperations in the A-mode may be performed by a corrected drivingfrequency in a stable condition.

According to an example embodiment, determination of an error in theinduction heating fusing device 1′ based on a current phase may beperformed in the B-mode. Furthermore, determination of an error in theinduction heating fusing device 1′ based on a power consumption valuemay be performed together.

Referring to FIG. 10, when it is determined by operations S1002 and S409that the induction heating fusing device 1′ has an error, a stop processis performed, but an operation in the B-mode may be performed instead ofthe stop process.

FIG. 11 illustrates a flowchart of a driving process performed in aninduction heating fusing device, according to an example embodiment.

As illustrated in FIG. 11, when it is determined that the inductionheating fusing device 1′ has an error, an operation in the B-mode may beperformed in the induction heating fusing device 1′. Due to theoperation in the B-mode, a printing operation in the A-mode may bepaused, and the printing operation in the A-mode may be resumed when itis determined that the device is in a stable or normal condition in theB-mode.

The induction heating fusing device may be provided with an imageforming apparatus such as a laser printer, and may be used to fuse toneronto paper in the laser printer.

FIG. 12 illustrates an image forming apparatus according to an exampleembodiment.

According to an example embodiment, the image forming apparatus 1000forms an image by fusing toner onto paper, and may be a laser printer,but is not limited thereto.

The apparatus 1000 may include an induction heating fusing device 1100and an image former 1200.

The image former 1200 may form an image.

The induction heating fusing device 1100 may fuse the image, formed bythe image former 1200, onto paper.

The induction heating fusing device 1100 may include a controller 1110,a driver circuit 1120, and a resonance circuit 1130. The inductionheating fusing device 1100 may be the aforementioned induction heatingfusing devices 100 a, 100 b, 1, or 1′, but is not limited thereto.

The controller 1110 may correspond to the aforementioned controller 10.The driver circuit 1120 may correspond to the aforementioned drivercircuits 23, 20, or 30. The resonance circuit may correspond to theaforementioned resonance circuit including the capacitor 15 and the coil16.

Explanations of the induction heating fusing devices 100 a, 100 b, 1,and 1′ may be applied to the induction heating fusing device 1000, andthus a redundant explanation is omitted.

According to an example embodiment, the image forming apparatus 1000 mayoperate in a stable condition due to the aforementioned methods of errordetermination.

All references including publications, patent applications, and patents,cited herein, are hereby incorporated by reference to the same extent asif each reference were individually and specifically indicated to beincorporated by reference and were set forth in its entirety herein.

Various embodiments of the present disclosure may be embodied as on acomputer-readable recording medium including computer-readable codessuch as a program module executable at a computer. A computer-readablerecording medium may be volatile, non-volatile, or a combination ofvolatile and non-volatile, where appropriate. The computer-readablerecording medium includes a computer storage medium and communicationmedium. The computer storage medium may include a computer-readableinstruction, a data structure, a program module, or any medium, but isnot limited thereto. The communication medium may include anyinformation transmission medium such as a carrier wave.

The example embodiments may be represented using functional blockcomponents and various operations. Such functional blocks may berealized by any number of hardware and/or software components configuredto perform specified functions. For example, the example embodiments mayemploy various integrated circuit components, e.g., memory, processingelements, logic elements, look-up tables, and the like, which may carryout a variety of functions under control of at least one microprocessoror other control devices. As the elements of the example embodiments areimplemented using software programming or software elements, the exampleembodiments may be implemented with any programming or scriptinglanguage such as C, C++, Java, assembler, or the like, including variousalgorithms that are any combination of data structures, processes,routines or other programming elements. Functional aspects may berealized as an algorithm executed by at least one processor.Furthermore, the example embodiments concept may employ relatedtechniques for electronics configuration, signal processing, and/or dataprocessing. The terms ‘mechanism’, ‘element’, ‘means’, ‘configuration’,etc. are used broadly and are not limited to mechanical or physicalembodiments. These terms should be understood as including softwareroutines in conjunction with processors, etc.

Embodiments of the present disclosure should be understood as variousexamples, and should not be interpreted as limitation of embodiments.For the sake of brevity, related electronics, control systems, softwaredevelopment and other functional aspects of the systems may not bedescribed in detail. Furthermore, the lines or connecting elements shownin the appended drawings are intended to represent example functionalrelationships and/or physical or logical couplings between the variouselements. It should be noted that many alternative or additionalfunctional relationships, physical connections or logical connectionsmay be present in a practical device. Moreover, no item or component isessential to the practice of the example embodiments unless it isspecifically described as “essential” or “critical.”

The use of the terms “a”, “an”, and “the” and similar referents in thecontext of describing the example embodiments (especially in the contextof the following claims) are to be construed to cover both the singularand the plural. Furthermore, recitation of ranges of values herein aremerely intended to serve as a shorthand method of referring individuallyto each separate value falling within the range, unless otherwiseindicated herein, and each separate value is incorporated into thespecification as if it were individually recited herein. The operationsof all methods described herein can be performed in an appropriate orderunless otherwise indicated herein or otherwise clearly contradicted bycontext. The example embodiments are not limited by an order in whichthe operations are described herein. The use of any and all examples, orexample language (e.g., “such as”) provided herein, is intended merelyto clearly describe the example embodiments and does not pose alimitation on the example embodiments unless otherwise claimed. Numerousmodifications and adaptations will be readily apparent to those skilledin this art without departing from the spirit and scope of the exampleembodiments.

1. An image forming apparatus, comprising: an image former that forms animage on printing paper; and an induction heating fusing device thatfuses the image onto the printing paper and comprises: a resonancecircuit comprising an inductor that is inductively heated by a currentto generate fusing heat; a driver circuit that applies a current to theresonance circuit; and a controller configured to drive the drivercircuit in an A-mode in which a fusing operation is performed, and todetermine whether the apparatus has an error in a B-mode in whichmagnitude of the current applied to the resonance circuit by the drivercircuit is limited to less than a preset level.
 2. The apparatus ofclaim 1, wherein the controller is configured to drive the drivercircuit in the A-mode when it is determined in the B-mode that theapparatus does not have an error.
 3. The apparatus of claim 1, whereinthe driver circuit is supplied with power from different power sourcesrespectively in the A-mode and the B-mode.
 4. The apparatus of claim 1,wherein the driver circuit comprises a first driver circuit and a seconddriver circuit, the first driver circuit is driven in the A-mode, andthe second driver circuit is driven in the B-mode.
 5. The apparatus ofclaim 4, wherein the driver circuit is alternatively electricallyconnected to the first driver circuit in the A-mode and the seconddriver circuit in the B-mode.
 6. The apparatus of claim 4, wherein thefirst driver circuit is electrically separated from the second drivercircuit, the first driver circuit is electrically open in the B-mode,and the second driver circuit is electrically open in the A-mode.
 7. Theapparatus of claim 1, wherein the controller is configured to determinewhether the apparatus has an error based on a power consumption value ofat least one of the resonance circuit and the driver circuit.
 8. Theapparatus of claim 7, wherein the driver circuit is driven in the B-modebased on a first frequency and a second frequency, and the powerconsumption value comprises: a first power consumption value that isestimated when the driver circuit is driven at the first frequency; anda second power consumption value that is estimated when the drivercircuit is driven at the second frequency.
 9. The apparatus of claim 8,wherein the controller is configured to determine whether the apparatushas an error based on an inclination measured based on the firstfrequency, the first power consumption value, the second frequency, andthe second power consumption value.
 10. The apparatus of claim 8,wherein the driver circuit is driven in the A-mode at a drivingfrequency within a predetermined range, and the first frequency and thesecond frequency is within the predetermined range.
 11. The apparatus ofclaim 1, wherein the controller is configured to determine whether theapparatus has an error based on a phase of a current in the resonancecircuit.
 12. The apparatus of claim 11, wherein the phase of the currentin the driver circuit is detected periodically based on a clock of thecontroller.
 13. The apparatus of claim 1, wherein the controller isfurther configured to determine whether the apparatus has an error inthe A-mode, and to stop driving the driver circuit in the A-mode when itis determined that the apparatus has an error.
 14. The apparatus ofclaim 13, wherein the controller is configured to drive the drivercircuit in the B-mode to determine whether the apparatus has an errorwhen the controller stops driving the driver circuit in the A-mode. 15.The apparatus of claim 1, wherein a driving frequency of the drivercircuit in the A-mode is determined based on a power consumption valueof at least one of the resonance circuit and the driver circuit.
 16. Theapparatus of claim 1, wherein a driving frequency of the driver circuitin the A-mode is determined based on a phase of a current in theresonance circuit.
 17. A method performed by an image forming apparatus,the image forming apparatus comprising: an image former that forms animage on printing paper; and an induction heating fusing device thatfuses the image onto the printing paper and comprises: a resonancecircuit comprising an inductor that is inductively heated by a currentto generate fusing heat; and a driver circuit that applies a current tothe resonance circuit, wherein the method comprises: determining whetherthe apparatus has an error in a B-mode in which magnitude of the currentapplied to the resonance circuit by the driver circuit is limited toless than a preset level; and driving the driver circuit in an A-mode inwhich a fusing operation is performed when it is determined that theapparatus does not have an error in the B-mode.
 18. The method of claim17, wherein the driver circuit comprises a first driver circuit and asecond driver circuit, the first driver circuit is driven in the A-mode,and the second driver circuit is driven in the B-mode.
 19. The method ofclaim 17, wherein the determining comprises: determining whether theapparatus has an error based on a power consumption value of at leastone of the resonance circuit and the driver circuit.
 20. The method ofclaim 17, wherein the determining comprises: determining whether theapparatus has an error based on a phase of a current in the resonancecircuit.